This invention relates to a rolling bearing unit having a rolling bearing attached to the outer periphery of a shaft body such as a vehicle-use hub unit.
The vehicle-use hub unit, in general, has a hub wheel and a double row rolling bearing. The rolling bearing is mounted on the outer periphery of the shaft body of a hub wheel so as not to slip off the shaft body.
The shaft body of the hub wheel has on its free end side a cylindrical portion used for preventing the bearing from slipping off the shaft body. The cylindrical portion is bent and deformed outward in a radial direction using a caulking jig to be caulked onto an axial outer end face of an inner ring of the bearing. Thereby the cylindrical portion forms a caulking portion. The caulking portion prevents the bearing from slipping off the hub wheel. At the same time, a pre-load is applied from the caulking portion to the inner ring of the bearing. Carbon steel is used as the material of the inner ring of the bearing.
In order to enhance the life of the bearing, the inner ring is heat-treated to increase the strength of a raceway surface thereof.